A transformed TLM formulation for adjoint variable-based sensitivity analysis

We present a transformed formulation for the transmission-line modeling (TLM) method with nondispersive boundaries. This formulation enables efficient adjoint variable-based sensitivity analysis of lossless electromagnetic structures. The TLM simulation is cast in a form common to both the original and adjoint simulations. The same TLM simulator is used for both the original and adjoint problems with the only difference in the sources. Our proposed formulation is illustrated through estimating objective function sensitivities with respect to the physical dimensions of waveguide discontinuities.